The S&P 500 is now up more than 5.5% in 2014 after surprising much of Wall Street Monday by finishing above 1,950 for the first time following an uneven trading session. While bears in early February warned that the S&P 500 had dropped below its 50-day moving average, and again on April 10, the benchmark index continues to make new highs, though on less and less volume.

Bearish contrarians remain on full alert, but "we've been running with the bulls, and continue to do so," Ed Yardeni, the New York-based chief investment strategist at Yardeni Research, wrote in a note. "However, we see the same old reasons for doing so." The major central banks continue to pump liquidity into financial markets, and while some of that liquidity is boosting economic growth, much of it is inflating asset values. And while economic growth has been "subpar" in both the U.S. and overseas during the current bull market, earnings have been very strong.

The forward earnings of the S&P 500 rose to new record highs last week, and at a faster pace in recent weeks, according to Yardeni Research.

Stocks to watch Tuesday include Time Warner , Facebook and eBay, and Walmart. Time Warner is in talks to buy a large stake in Vice Media for as much as $1 billion, a deal that could include providing Vice with the television network HLN, people with knowledge of the negotiations told The New York Times. David Marcus, the head of eBay's PayPal unit, is leaving the company for Facebook, where he'll lead mobile messaging products. Joel Anderson, chief executive of Walmart.com in the U.S., is leaving later this month for a job at a new company, according to a memo sent to Walmart employees on Monday, The Wall Street Journal reported.

The economic calendar in the U.S. on Tuesday includes wholesale inventories for April at 10 a.m. EDT.

European stocks paused for breath on Tuesday, with U.K. indices losing ground as news of strong industrial output increased the chances of a near-term rate rise. Asian indices took their cue from Wall Street and closed largely in the green, though Japanese markets retreated as the yen rose.